Leaded steel fume control



Jan. 26, 1965 J, D. FRITZ ETAL 3,166,805

LEADED STEEL FUME CONTROL Filed Jan. 15. 196s INVENTORS JAMES D. FRITZ KRT K. KLEIN 0MM/6., Www/9mm ATTORNEYS United States Patent() 3,166,805LEADED STEEL FUME CONTROL James D. Fritz, Tonawanda, and Kurt K. Klein,Buffalo,

N.Y., assignors to The Colorado Fuel and Iron Corporation, Denver,Cold., a corporation of Colorado Fiied'}an. 15, 1963, Ser. No'. 251,538

- 6- Claims.` (Cl. 22-139) This invention relates to the production ofleaded steel in ingot casting operations, and has for its object theprovision of an improved apparatus and process for controlling the leadoxide fumes emitted from such operations. More particularly, theinvention is concerned with bottom poured leaded steel ingots andprovides means on the top of the ingot mold having means to absorb thelead oxide fumes.

The introduction of lead into ingot steel results in some of the leadbeing oxidized and released into the Working area as a toxic fume. Thishas resulted in the use of hoods, exhaust fans and associated equipmentto prevent or minimize the inhalation of the toxic fumes by workmen.Such equipment is expensive and not practical for small steel producers.

Our invention provides a very simple and inexpensive means forpreventing the release of the toxic fumes from each ingot mold into thesurrounding atmosphere. In accordance with our invention, We provide asand cap on the top of the ingot mold, especially molds for bottompoured ingots, which contains a sand layer or bed into which the toxicfumes can enter and be absorbed. By absorbed we mean that the lead oxidedoes not escape from the sand and is retained either because of achemical reaction or a combination of chemical and physical conditionswhich retain the lead in or on the sand. The lead oxide may be convertedto a harmless neutral salt. At the temperature of the sand which is inexcess of l000 F. the lead oxide can react with corn-` ponents of thesand and be prevented from entering the atmosphere. We have found thatsilica sand is a preferred kind of sand which lead oxide reacts with atthe high temperatures attained to form lead silicate. However, we maysupplement the sand with a material reactable with lead oxide, such assilicon or silicon alloys, or exothermic compositions containingsilicon, nitrates and the like. The silicon seems to have a catalyticeifect and the exothermic composition increases the temperature andreactivity. The sand bed may include paper, wood or asbestos to aid incontrolling the direction of the lead oxide fumes into the sand bed. Thesand bed may be regarded as a ilter which absorbs or renders harmlessthe lead oxide fumes leaving the top of the ingot mold.

A preferred apparatus of the invention comprises a confining structure(hereinafter called a cap) advantageously mounted over a hot top formaking close contact with the top of the ingot mold. The cap isconstructed to hold in position a layer of sand of sutiicient depth toserve as a sort of filter bed having the requisite porosity for the leadfumes to enter and become absorbed. ln a preferred embodiment the cap issealed where it engages the ingot mold and the sand is supported on ascreen which permits free entry of the lead oxide fumes.

These and other novel `features of the invention will be betterunderstood after considering the drawings and the following discussion:

FIG. 1 is a perspective, partly in section, of an ingot mold for abottom poured ingot and a cap in accordance with the invention; and

FIG. 2 is a sectional elevation of another embodiment of the invention.

g"lee The apparatus illustrated in FIG. 1 comprises an ordinarybottompour ingot mold 1, usually formed of top of the hot-top kandmaking a fairly close contact.

The flange 5 is sufficiently above the lower edge of the frame as toform a depending skirt 6 which forms a pocket 7 at the top of thehot-top for inserting sealing clay. This skirt also serves to center thecap over the hot-top. A grating 8 is placed upon the iiange 5 to givesupport to a metal screen 9 such as a copper screen. The bed of porous,loose sand 12 which effects the removal of lead fumes is placed upon andis supported by the screen. The bed of sand is suiiiciently deep, forexample about twelve inches, that very little, if any, of the lead oxidefumes will pass completely through and contaminate the atmosphere.

FIG. 2 illustrates another modification of the invention comprising aningot mold 15 for a bottom poured leaded ingot having fitted inside thetop a hot-top of a type widely used and known as a C & D hot-top. Thishot-top comprises outer supporting parts 16 and 17 formed of steel oriron, which are usually bolted together, an inner pre-formed brick liner18 and a slurry Wash 19. A sand ring 20 is clamped on the bottom. Thejoint between the hot-top and the ingot mold is sealed with.

lire clay 20' and the joint between the hot-top and the cap is sealedwith fire clay 21.

The steel sand cap 22 of the invention comprisesia rectangular wall 23,a transverse flange 24 which rests on thc top of the hot-top and adepending skirt 25 which lits closely against the inside of the hot-topto hold it in centered position. A steel grid 26 is placed over theiange 24 and the grid supports a screen 27 formed of metal such ascopper. The silicasand bed 28 may be any suitable depth, say, up toabout 12 inches, but in any event, is suiiicient to remove all the leadoxide fumes. The sand bed can be heated to temperatures above 1000" F.by the heat from the ingot and it has been found that the lead oxide ischanged to a lead salt at this or higher temperatures, possibly inreaction with the silica to form a lead silicate. We may also mix withthe sand a suitable form of silicon such as the to 98% silicon ofcommerce whichseerns to have a catalytic eiiect and may even enter intodirect reaction with the lead oxide. We may also add to the sand amixture of silicon and an oxidizing agent such as sodium nitrate toprovide an exothermic reaction which increases the temperature of thesand bed and also the reactivity of silica and silicon with lead oxide.

chemical reaction but some may be physically absorbed Y and We,accordingly, referto the removal of the lead oxide by either or bothmeans as absorption.

We claim:

l. The process for preventing the release of toxic lead oxide fumes intothe working area from an ingot mold in the production of leaded steelwhich comprises'introducing molten leaded steel into an ingot mold fromwhich lead oxide fumes are released, placing over the ingot moldcontaining the molten leaded steel a bed of sand supported over andclosing the opening of the mold, said sand containing silica into whichthe fumes enter, and absorbing the lead oxide fumes in the bed ofsilica.

2. In the process of claim 1 providing a bed of sand which containsavmaterial of the group consisting of silicon and an alloy of silicon toreact with the lead oxide.

ing agent.

4. The combination with an ingot mold for bottom poured leaded steelingots which comprises a hot-top fmounted on the top of the ingot mold,a cap removably mounted on the hot-top, a screen in the cap, a bed of4porous sand in the cap supported by the screen closing 'the opening ofthe hot-top, whereby lead oxide fumes from the ingot -are absorbed inthe sand.

Y 5. The combination defined in claim 4 which comprises a grid overlyingthe hot-tops on which the screen is supported. 1

. 4 metal screen, a bed of sand mounted on the screen, said cap and sandproviding a closure for the hot-top whereby fumes released from theingot enter and are absorbed by the sand.

References Cited by the Examiner UNITED STATES PATENTS 929,688 8/09Monnot 22-139 1,920,854 8/33 Gathrnann 22-139 XR 1,928,996 10/34Gathmann 22--139 XR 2,197,259 4/40 Nead 75-129 FOREIGN PATENTS 583,0189/59 Canada.

MICHAEL V. BRINDISI, Primary Examiner.

ROBERT F. WHITE, Examiner.

1. THE PROCESS FOR PREVENTING THE RELEASE OF TOXIC LEAD OXIDE FUMES INTOTHE WORKING AREA FROM AN INGOT MOLD IN THE PRODUCTION OF LEADED STEELWHICH COMPRISES INTRODUCING MOLTEN LEADED STEEL INTO AN INGOT MOLD FROMWHICH LEAD OXIDE FUMES ARE RELEASED, PLACING OVER THE INGOT MOLDCONTAINING THE MOLTEN LEADED STEEL A BED OF SAND SUPPORTED OVER ANDCLOSING THE OPENING OF THE MOLD, SAID SAND CONTAINING SILICA INTO WHICHTHE FUMES ENTER, AND ABSORBING THE LEAD OXIDE FUMES IN THE BED OFSILICA.